Windows Deliver a Lot More Than Just Light and Air

We have said it before: windows are hard. They are particularly hard in northern countries like Sweden, where during winter the days are short and the sun is very low in the sky. Window design in cold climates is a technical balancing act. You want it big to get the light, but you want it small to minimize the heat loss. But there is so much more that windows have to do for our social and emotional well-being. Perhaps that's why they play such an outsized role in the paintings of Sweden's Carl Larssen.

A recent study published in Buildings and Cities—"Windows: a study of residents’ perceptions and uses in Sweden"—looks at the many roles that windows play and the way people use them, exploring "daylight, the visual connection to the outside and the role of windows in the home during the day and night." But windows do much more than just provide light and air: "Windows represent an enjoyment of the home and fulfil much more than physical needs. They must allow sufficient personal control over fresh and cool air, sound, sunlight, streetlighting and privacy."

The study authors, Kiran Maini Gerhardsson and Thorbjörn Laike, interviewed occupants (aged 24 to 93 years old, half men and half women) living in multi-family dwellings. They showed them 25 windows and asked them to assign keywords to each. They followed up with home visits and checked out the windows the participants had in their units and asked a simple question: "Imagine the window opening has been blocked up and there is no window anymore. How would it affect your use of the room and your dwelling—during the day and night?"

Windows turned out to be very important for occupant comfort, for visual connection to the outside. But they also had to be able to be screened for privacy; sometimes these conflicted. Sometimes the sill height was important. One occupant was going to add some frosted film to the bottom of his window: "I don’t want to see their faces when I’m sitting down, but when I’m standing and see their faces, I can wave to them."

Interviewees preferred daylight to artificial light for many reasons, including as a time indicator, and "because it varies, increases room brightness and improves mood." This is the principle of the circadian rhythm covered on Treehugger before: Our bodies need the change from red to blue and back to red. Windows are also demonstrations of autonomy, something that people can adjust to meet their own personal requirements and tastes.

"Windows, transparent in both directions, enable the environmental conditions (social connection) to support the basic need for relatedness. For example, by following ‘window blind etiquette’, people show they care for others or want to be accepted by others. Autonomy is represented by participants’ own decisions on when to adjust daylight controls (blinds, curtains, external shades) to improve sleep, daylight or privacy. Even if others are indirectly involved in ‘window blind etiquette’, residents may endorse such values, and the chosen actions will still be an expression of the self. "

There are practical conclusions, such as "housing designers and developers are advised to include exterior shading devices in the design and optional indoor window treatment on construction to facilitate sustainable shading and privacy solutions." In the face of climate change, there should be solar shading and lots of ventilation. There should be windows in every room except the bathroom or kitchen: "One could go even further and require a view to the outside of the sky and/or the ground. One consequence is that the height of the windowsill in apartments above the ground floor should allow a view over public paths and places."

The authors conclude windows serve many functions that go beyond just light and air and should be designed accordingly.

"There is much more to such experiences than the satisfaction of physical needs (modulating indoor temperatures, blocking exterior noise or enabling visual tasks). Perceiving a room to be adequately daylit, pleasant and spacious seems to be equally essential, and a view of the world outside brings information to inhabitants. However, windows also need to screen the gaze of people outside from peering in, moderate bright sunlight during the day."

We Are Doing Windows All Wrong

I learned about this study via a tweet from Fionn Stevenson, professor of sustainable design at the University of Sheffield School of Architecture, noting how awful the windows are in the United Kingdom. I suspect that they are worse in North America. I have written before about how hard windows have to work, describing one from 1810:

"In 1810 glass was really expensive, so even though there was not much artificial light, they made them as small as they could and still get enough light to see. They were double-hung so that you could tune them for maximum ventilation. They had shutters for security and privacy while maintaining ventilation, and interior sheer blinds to cut glare. There is an overhanging cornice to keep the rain off so that they would last longer. There would be two in every room for cross-ventilation, and heavy drapes in for keeping the heat in during winter. This was a hard-working, carefully thought-out piece of climate control. There is not a motor to be seen and 200 years later, it still works."

Later, as we learned about Passivhaus, we found windows had to be built, sized, and tuned to seal tight when closed, with appropriate glass to admit or reject infrared, and be insulated as well as a wall.

Now Gerhardsson and Laike add a few more layers of complexity and sophistication, how the window affects people inside and out.

So much complexity, so many considerations. There is so much talk these days about "smart windows" but the smartest window of all is the one that is built the right way, to the right size, in the right place,